debug please

Question

program deb;
uses crt;
const
n=100;
var
a: array[1..n] of integer;
b,i,j:integer;
begin
a:=20;
randomize;
writeln ('new masiv');
for i:=1 to n do
begin
a[i]:=Random(100);
write(a[i], ' ');
end;
writeln;
for i:=3 to n-1 do
a:=-5;
for j:=1 to n-i do
if a[j] mod 20 then
begin
b:=a[j];
a[j]:=a[i+1];
end;
writeln('sort masiv');
for i:=1 to n do
write(a[i]: ' ');
end.

Answer 1

now you can improve this sort algorithm as you wish
https://pastebin.com/PUVM6sNa